ANSWER KEY
Mendelian Genetics Problem Set 1: Basic Genetics Problems
1. In pea plants, yellow peas are dominant to green peas and purple flowers are dominant to white
flowers. For each of the following parental crosses, give the predicted phenotypic and genotypic ratios
of the F1 generation:
1. (heterozygous purple-flowered) x (heterozygous purple-flowered)
P: 3 Purple: 1 White
G: 1 PP: 2Pp: 1pp
2. (true breeding white-flowered, yellow pea) x (true breeding purple-flowered, green pea)
P: All Purple, Yellow
G: All PpYy
3. (heterozygous purple-flowered, yellow pea) x (heterozygous purple-flowered, yellow pea)
P: 9 Purple, Yellow: 3 Purple, Green: 3 White, yellow: 1 White, Green
2. You have a purple-flowered pea plant. You do not know its genotype. Diagram the test-cross you
would conduct to determine the plant’s genotype and what results you would expect if the plant was
heterozygous and if the plant was homozygous
Test cross (1): Pp x pp  50% Purple, 50% White
Test cross (2): PP x pp  100% Purple
3. You are studying five traits in Pentids, an amazonian flying beetle. You have identified each trait as
belonging to separate alleles located on separate chromosomes and have categorized those alleles as
A,B,C,D, and E, respectively. After years of controlled breeding experiments, you have developed your
Pentid lines to the point where you can control their genotypes with certainty. You perform the
following cross:
P:
(AaBbCcDdEe) x (AAbbCCDdEe)
Predict the probability of recovering offspring of each of the following genotypes from this parental
cross:
i.
ii.
iii.
iv.
AaBbCcDdEe
AAbbCCDDee
AaBbCCDdEe
AaBbccDdee
1/32
1/128
1/32
0
ANSWER KEY
Mendelian Genetics Problem Set 2: Extended
1. In cattle, roan coat color is an example of an autosomal, co-dominant phenotype. Roan (CrCw) cattle
are produced from the mating of a white (CwCw) cow to a red cow (CrCr). Predict the phenotypic and
genotypic frequencies of offspring from each of the following crosses:
1. Roan x White
3. Red x White
P: 50% Roan, 50% White
P: 100% Roan
G: 50% CrCw, 50% CwCw
G: 100% CrCw
2. Roan x Red
P: 50% Red, 50% Roan
G: 50% CrCr, 50% CrCw
4. Roan x Roan
P: 25% Red, 50% Roan, 25% White
G: 25% CrCr, 50% CrCw, 25% CwCw
2. A man who has type O blood marries a woman who is type AB. What are the chances that their child
will have each of the following blood types?
1. Type A 50%
4. Type O 0%
2. What is the probability that they will have a Type A son and a Type B Daughter? 12.5%
3. Type B 50%
3. Red-Green color blindness is inherited as an X-linked recessive trait in humans. A woman, who’s
mother had red-green color blindness marries a color blind man. What are the chances that their child
will be:
1. a color-blind male? 25% 4. a normal male? 25%
2. a color blind female? 25% 5. a normal female? 25%
3. The couple has a color blind male. What are the chances that their next child will be a normal
female? 25%
4. You have conducted exhaustive experiments studying the inheritance of four genes (A,B,C and D) that
are all on chromosome 3 in Drosophila melanogaster. You have recorded the following frequencies of
recombination in offspring for each of the genes:
Gene pair:
Frequency of Recombination:
ab
20
ac
28
ad
5
bc
10
bd
15
cd
24
1. What is the order of the genes on the chromosome?
A-D-B-C
2. Why is the distance between genes a and c as shown in the data smaller than the distance that
is indicated by summing the smaller distances?
Possibility of Crossing Over